Handheld power tools having a gear unit, in particular, a planetary gear unit, such as a straight screwdriver, a cordless drill/driver or a drill, include, generally, a safety coupling adjustable by the operator, so that the handheld power tool does not continue to rotate uncontrollably in response to a predetermined torque being exceeded. Thus, German Patent Application No. DE 197 37 234 A1 describes a tool having a rotatable tool support, the tool support being drivable by a drive motor via a planetary gear unit, and the ring gear of the planetary gear unit interacting with the gear housing via a slip clutch in such a manner, that a pressure plate moves away from the clutch upon the reaching of an adjustable torque, which means that a movement of the ring gear relative to the gear housing triggers a movement of the ring gear relative to the gear housing.
In addition, conventional handheld power tools may include mechanical and/or electrical switches to detect the relative movement of the ring gear, may generate an electrical signal, and disconnect the current supply to the motor.
A disadvantage is that due to the elasticity of the component parts used, in response to unfavorable working situations in which loads and vibrations suddenly occur, electrical signals are generated, and the current supply to the motor is interrupted, although no relative movement of the ring gear has occurred.